Device for determining and monitoring the level of a medium in a container

Abstract

The invention relates to an apparatus ( 1 ) for ascertaining and monitoring fill level ( 2 ) of a medium ( 3 ) in a container ( 4 ) by means of a travel-time measuring method of high-frequency measurement signals ( 6 ) with a horn antenna ( 7 ) having a waveguide section ( 8 ), a flared, horn section ( 9 ) and a cavity ( 11 ) filled, at least partially, with a dielectric filling body ( 12 ). Object of the invention is to provide a simple, temperature-stable, horn antenna filled with a dielectric material.

The invention claimed is: 
     
       1. An apparatus for ascertaining and monitoring the fill level of a medium in a container by means of a travel-time measuring method of high-frequency measuring signals, comprising:
 a horn antenna having a waveguide section, a flared, horn section, and a cavity filled, at least partially, with a dielectric filling body, wherein a defined separation is provided in said flared, horn section between the inner surface of said horn antenna and the outer surface of said dielectric filling body for compensating different thermal expansions of said dielectric filling body and said horn antenna, and 
 at least one sealing element or oat least one locking element between said filling body and said horn antenna is provided for performing a sealing function and, simultaneously, a locking of said filling body in said horn antenna, wherein: 
 an outer surface of said filing body lies directly against the inner surface of said horn antenna over a certain length for pressure-resistance purposes, with an encircling ridge being formed for stabilizing the position of said filling body relative to the central axis; and 
 said sealing element or said locking element is placed in said waveguide section between said horn antenna and said filling body. 
 
     
     
       2. The apparatus as claimed in  claim 1 , wherein:
 by said defined separation, a gap of 0.2-2 mm is formed between the inner surface of said horn antenna and the outer surface of said dielectric filling body. 
 
     
     
       3. The apparatus as claimed in  claim 1 , wherein:
 said defined separation between the inner surface of said horn antenna and the outer surface of said dielectric filling body is constant. 
 
     
     
       4. The apparatus as claimed in  claim 1 , wherein:
 said defined separation is interrupted periodically, or arbitrarily, so that the at least one ridge or at least one surface structure is formed on the outer surface of said filling body and/or on the inner surface of said horn antenna adjoining one another or separated from one another. 
 
     
     
       5. The apparatus as claimed in  claim 1 , further comprising:
 an attenuating foil absorbing the high-frequency measuring signal in said defined separation between the inner surface of the horn antenna and the outer surface of said dielectric filling body. 
 
     
     
       6. The apparatus as claimed in  claim 5 , wherein:
 a shape transition of said filling body from said flared horn section to said disk-shaped widening as a flange plate is continuously rounded, for preventing a notch effect in said filling body in the region of said shape transition. 
 
     
     
       7. The apparatus as claimed in  claim 1 , wherein:
 a disk-shaped widening as a flange plate is formed on the end of said filling body facing the process space. 
 
     
     
       8. The apparatus as claimed in  claim 1 , wherein:
 said filling body or said horn antenna is multi-piece or it is formed of a plurality of different materials. 
 
     
     
       9. The apparatus as claimed in  claim 1 , wherein:
 said filling body has in the radiation direction one of: a convex, concave, conical or Fresnel lens shape.